Shop Talk Blog

The Official Blog for Texas Final Drive

Final Drive Leaks


One of the first signs of trouble with a final drive may be the presence of fluid where it shouldn’t be. Leaks will lead to final drive failure. In this Shop Talk Blog post, we are going to discuss how to identify possible sources of leaks and the types of fluid involved.

Sources of Final Drive Leaks

If your final drive is leaking, it's going to be leaking one of two things: gear oil, or hydraulic fluid. Gear oils leaks occur on the planetary side of the final drive and, as you might have guessed, hydraulic fluid leaks occur on the hydraulics side. Let's take a look at each of these.




Leaks on the Hydraulics Side of a Final Drive

Hydraulic fluid is thinner, with a consistency similar to brake fluid. With a hydraulic leak, you either have a hose leak or a problem in the hydraulics section of your final drive. One of most common causes of a hydraulic leak is a clogged case drain filter. A clogged case drain filter can cause the internal seals to blow and the final drive to start leaking hydraulic fluid. If left unaddressed, this will lead to catastrophic failure and a totaled final drive. If contamination makes it way in because of a leaking seal, it can affect your entire hydraulic system.

Leaks on the Planetary Side of a Final Drive

If the leaking fluid is thick, then it is most likely going to be gear oil. Gear oil will leak from the planetary side of the final drive where the gear hub is located. You can detect this type of leak by checking for fluid dripping on the tracks or present behind the sprocket. If you frequently need to top off the gear oil to keep it at an acceptable level, that is another indicator of a gear oil leak.


Problems in the planetary side are usually accompanied by severe grinding noises followed by the final drive locking up. If your track drive is leaking oil near where the sprocket mounts, this means that the mechanical face seal (also known as the floating face seal or duo-cone seal) has failed. It needs to be replaced ASAP, because if gear oil can get out then debris can get in. Debris in your final drive means costly repair and major damage to gears, axles, and bearings.

Note, however, that there are on average about two quarts of gear oil contained in the front of the drive. A very large quantity of fluid would indicate a problem with the hydraulics side rather than with the planetary side.



What To Do If Your Final Drive Is Leaking

If your final drive is leaking, determine what type of leak it is (gear oil or hydraulic fluid) and track down the source of the leak. Once you know where the leak is coming from, send it in for diagnosis and repair. All it probably needs it the replacement of a few seals if you catch the leak early on. If you neglect the leak, then you will be looking at more extensive repairs.



Regardless of whether your problem is on the hydraulics side or the planetary side, leaks must be attended to before severe damage occurs. Never neglect those leaks! The longer you ignore a leak, the more extensive the damage and the more expensive the repairs.  Consider tracking down those leaks another part of regular final drive maintenance.


Texas Final Drive is your partner in providing new or remanufactured final drive hydraulic motors from a single mini-excavator to a fleet of heavy equipment. Call today so we can find the right final drive or hydraulic component for you, or check out our online store to find your O.E.M. manufacturer brand motor now.

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Topics: Final Drive, Final Drive Failure, Final Drive Motor Maintenance, Final Drive Maintenance, Mini-excavators, Compact Excavators, Leaks

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